1. Field of the Invention
The present invention relates to a compound eye camera capable of picking up and displaying a stereoscopic image and a two-dimensional image, and also to an image display system utilizing such compound eye camera.
2. Related Background Art
For picking up and displaying a stereoscopic image, there is already known, for example, a stereoscopic television apparatus as disclosed in the Japanese Patent Application Laid-Open No. 62-21396, in which a set of images with parallax is obtained from plural cameras and presented to the operator as a stereoscopic image by stereoscopic display on a stereoscopic image display apparatus designed exclusively for the system. Such a stereoscopic image display system is generally composed of a camera for image pickup and a separate display apparatus for displaying the stereoscopic image, and, in general, after the image is picked up with the camera separate from the display, the picked-up image is displayed and edited on the display.
Also for obtaining the stereoscopic display, there is known a stereoscopic television system in which the image for the right eye and that for the left eye are respectively given different polarized states of light and are separated by polarizing spectacles. More specifically, a liquid crystal shutter is provided on the shutter and the polarizing state is switched in synchronization with the field signal of the image displayed on the display for obtaining different polarized states, and the observer wears the polarizing spectacles whereby the left- and right-eye images are respectively separated for the left and right eyes on a time-shared basis to enable stereoscopic observation. This method, however, has been associated with a drawback that the observer always has to wear the polarizing spectacles.
For obtaining stereoscopic display without the polarizing spectacles, there is known a system of providing a lenticular lens in front of the display, thereby spatially separating images for the left and right eyes. FIGS. 11A and 11B are schematic views of such stereoscopic display system employing a lenticular lens, wherein FIG. 11A is a cross-sectional view of the pixel display unit of a liquid crystal display, seen from above the observer, while FIG. 11B is a view showing the filter configuration of the pixel display unit.
The pixel display unit 60 shows displayed pixels of a liquid crystal display, of which the glass substrates, color filter, electrodes, polarizing plates, rear light source etc. are omitted. As shown in FIG. 11B, the pixel display unit 60 is composed of apertures 61 constituting pixels and provided with color filters and a black matrix 62 for separating the pixels. On the display surface of the liquid crystal display, there is provided a lenticular lens 63 consisting of cylindrical lenses having a semicircular cross section and extending perpendicularly to the plane of the drawing, and the pixel display unit 60 of the liquid crystal display is positioned at the focal plane of the lenticular lens. On the pixel display unit 60, right-eye images (R) and left-eye images (L) are alternately positioned in paired stripes each of which corresponds to a pitch of the lenticular lens 63 as illustrated and are focused, in optically separate manner, respectively on the right eye E.sub.R, E.sub.L by the lenticular lens 63 whereby the stereoscopic observation is rendered possible.
FIG. 11A only illustrates the spatial areas where the left-eye image and the right-eye image can be respectively observed by the lenticular lens at the central part of the display, but the spatial areas separated for the left- and right-eye images similarly exist for other parts of the lenticular lens and these areas overlap at the left and right eyes of the observer whereby the left- and right-eye images can be separately observed over the entire displayed image.
In addition to the foregoing, there are known other stereoscopic image display systems such as those disclosed in the Japanese Patent Application Laid-Open Nos. 5-107663 and 7-234459. As an example, FIGS. 12A to 12C show the basic configuration of a stereoscopic image display apparatus disclosed in the Japanese Patent Application Laid-Open No. 7-234459.
This stereoscopic image display apparatus is composed of a light directionality switching device 72 consisting of a matrix planar light source 70 and a lenticular lens 71, and a transmission display device 73. When a stripe-shaped light source for the right eye (70R in FIG. 12B) is turned on, a right-eye image (73R in FIG. 12C) is displayed in synchronization by an odd-numbered frame (field), and, when a stripe-shaped light source for the left eye (70L in FIG. 12B) is turned on, a left-eye image (73L in FIG. 12C) is displayed in synchronization by an even-numbered frame (field), whereby all the pixels can be utilized according to the even-numbered and odd-numbered frames (fields). In this case the pixels need not be divided.
In the conventional systems, as explained in the foregoing, the compound eye camera is separated from the stereoscopic display, and the compound eye camera itself is not provided with the function of displaying the stereoscopic image. For this reason, it is common to at first pick up the image with the camera which is separate from the display, and then to edit the picked-up image by displaying the same on the display device. In such operations, however, whether the obtained stereoscopic image is satisfactory can only be judged at the editing operation, and it has therefore been difficult to obtain a satisfactory stereoscopic image in a simple manner. For this reason, there has strongly been desired a compound eye camera provided with the display function.
Also in the above-mentioned conventional stereoscopic image display systems, there has not been considered the connection to the systems utilizing personal computer, which are the current mainstream of the image systems. Consequently, in case of fetching and displaying the stereoscopic image, picked up with the compound eye camera, in a personal computer, the user has to reconstruct the system anew and is therefore given a significant burden.
Also the aforementioned system employing the lenticular lens on the surface of the liquid crystal display for attaining the stereoscopic observation is associated with unsatisfactory image display because the image quality is deteriorated by the surface reflection of the lens etc., and the black matrix of the liquid crystal display generates Moire fringes. Also the aforementioned system employing time-shared display of the right-eye and left-eye images with parallax for attaining the stereoscopic observation has to effect high-speed switching of the images for avoiding flickering. For example Isono et al., "Condition for time-shared stereoscopic observation", Journal of Television Association, Vol. 41, No. 6, pp546-555 (1987) indicated that the stereoscopic observation could not be obtained in a time-shared system with a field (frame) frequency of 30 Hz. They also indicated that the limit frequency that does not give the flickering phenomenon when both eyes are alternately opened (called critical fusion frequency (CFF)) was about 55 Hz and that the field (frame) frequency has to be at least 110 Hz in consideration of the flickering. Consequently, in the conventional display systems, there is required a transmission display device capable of high-speed display. These drawbacks and limitations in the conventional stereoscopic display systems have to be picked up into consideration in providing the compound eye camera or the image display system with the stereoscopic display function.